This work is concerned with the organization of the eukaryotic genome and the nature and control of eukaryotic gene expression. To understand the nature of differential gene expression, clones have been synthesized starting with Triturus RNA from oocytes and somatic tissues. These are being hybridized in situ to lampbrush chromosome preparations in order to visualize those sequences which are being actively transcribed during oogenesis. In addition, such experiments should provide basic information regarding the nature of transcription during oogenesis - the minimal size of transcription units, the degree to which individual DNA sequences change their chromosomal structure during oogenesis, etc. We are also continuing to acquire basic information concerning the nature of the informational RNA stored during oogenesis and (presumably) used for protein synthesis after fertilization. We want to understand how these sequences are related to the nascent RNA molecules present on lampbrush chromosomes, how they are stored and how they interact with the protein synthetic machinery after (and before) fertilization.